Precipitation gradients, plant biogeography, and the incidence of drip-tips in Cerrado plant species

摘要

Examining how both climate and species distribution patterns correlate with leaf morphology can give insights into the ecological and evolutionary patterns that drive adaptive selection of leaf form and function. Drip-tips are a common feature of leaves in rain forest tree species; they are thought to be an adaptation that aids leaf drying and maximizes photosynthesis in areas with high-rainfall climates. We tested whether this macroecological pattern holds true across the precipitation gradients in a non-rain forest region-the woodland savannas of Brazil known as the Cerrado-and compared our results with previous studies from Amazonia. Drip-tips were, as expected, less common overall in the drier Cerrado than in Amazonia. In addition, within the Cerrado, drip-tips were more prevalent in areas with higher rainfall as well as in Cerrado sites that were closer to Amazonia. Moreover, species that occurred across both the Cerrado and Amazonia had drip-tips more often than species that were found only in the Cerrado. These findings support the hypothesis that drip-tips are adaptive and that either the cost of retaining drip-tips is low or that in drier regions they have other benefits.